The overall goal of this project is to gain information regarding the ability of hearing-impaired adults to group the many acoustic elements of speech into a coherent signal. This ability, termed perceptual coherence, is thought to be a fundamental aspect of speech perception, in which acoustic elements that share a common characteristic are grouped together and perceived as a single auditory event. During speech perception, for example, the vowel formants of a single talker may be grouped together by the common fundamental frequency. In normal-hearing adults, perceptual coherence has been found to promote the perception of speech in noise, including a background of multiple talkers. Although a number of studies have characterized the coherence of nonspeech stimuli in hearing impaired adults, the relation between perceptual coherence of speech and the characteristics of hearing loss has not been determined. The first aim of this project is to test the hypothesis that perceptual coherence of speech is poorer in hearing-impaired listeners relative to normal-hearing listeners and that coherence is reduced as a function of degree hearing loss. Results of this study should allow us to characterize the relation between hearing loss and perceptual coherence. The second aim is to test the hypothesis that low frequency acoustic information contributes significantly to the perceptual coherence of speech. This hypothesis is based on pilot data, which suggests that coherence decreases as hearing thresholds at 250 and 500 Hz increase. The results of this study should provide insight into the relative importance of low-frequency spectral and temporal information to the perception of speech. The third aim is to test the hypothesis that perceptual coherence is related to a listener's ability to perceive speech in noise. These results may improve our understanding of why hearing-impaired listeners have difficulty perceiving speech in degraded listening environments. [unreadable] [unreadable]